[llvm] [RegAlloc] Add a flag to toggle non-trivial rematerialization (PR #165630)

[Luke Lau via llvm-commits]

lukel97 wrote:

Before we add a flag for this, is it much trouble for you to carry this in your downstream? I'm wary of adding very specific flags for workarounds for downstream workloads. And ideally if possible we should aim to fix the compile time regression itself so the flag isn't needed.


https://github.com/llvm/llvm-project/pull/165630